A known hot shearing apparatus of the kind in question (U.S. Pat. No. 4,152,959) has the fixed shearing ring capable of being spread transversely of the shearing direction so as to avoid deformation of the front end of the bar in the shearing zone during the shearing process and to facilitate the advancing movement of the bar in the shearing rings.
The diameter of the movable shearing ring is greater than that of the stationary shearing ring in the unspread condition of the same. The spreading of the fixed shearing ring is limited to an extent which corresponds to the inner diameter of the movable shearing ring so as to prevent the bar entering the hot shearing apparatus from hitting against the front end of the movable shearing ring. In the position of maximum spread, the greatest inner diameter of the stationary shearing ring is flush with the bore of the undivided movable shearing ring.
The limitation of the spread to the inner diameter of the movable shearing ring is a disadvantage of this design. It is likewise disadvantageous that after being sheared that part of the bar which is located in the area of the undivided movable shearing ring remains unsupported in the direction of the shearing motion because there is a gap between the shearing ring bore and the surface of the bar. That leads to canting of the bar portion in question and accordingly to an oblique shearing cut.